The present invention relates to a semiconductor device having an identification number, and particularly to a technology for economically implementing a small-sized semiconductor device mountable to various objects.
An IC card for returning information in non-contact form by radio in response to an inquiry sent from an interrogator has actively been used in recent years. A small-sized semiconductor chip (IC) having a memory, a simple logic circuit, etc. has been built in the IC card. Each of semiconductor chips each having an identification number, which is similar to such a semiconductor chip as described above and is mountable to an object desired to perform identification in non-contact form, has been brought into sight. The semiconductor chips are respectively provided with read-only memories (ROM) in which identification numbers different every chips have been written.
A technology for implementing such a ROM has been disclosed in Japanese Patent Laid-open (Kokai) No. Hei 8-139208. According to the present method, identification numbers individually different from one another are written onto a semiconductor wafer every semiconductor chips by use of an electron-beam writing technology. Described specifically, the writing of the identification numbers is carried out by the cutting off of wiring patterns produced by electron-beam writing without having to use a glass mask.
According to the method, non-cut wiring patterns are temporarily formed by a photolithography process using the conventional glass mask as fixed patterns. Subsequently, a resist film is applied onto the semiconductor wafer and post-baked. Next, an electron beam is imaged or drawn onto a cut portion of the wiring pattern. Thereafter, a developer is used to remove the corresponding pattern at the electron-beam written portion. Further, a wiring at a predetermined portion of each wiring pattern is removed by etchant or dry-etching ions. Afterwards, the resist film is removed by an asher, followed by cleaning. Thus, it was necessary to pass a complex process for implementing patterning by the cutting of the originally intended wiring pattern.
As another method of providing ROM with identification numbers different every chips written therein, a technology for determining the presence or absence of contact holes according to an exposure process of a step-and-repeat system has been disclosed in Japanese Patent Laid-open (Kokai) No. Hei 10-55939.